1. Field
The present disclosure relates to optical films for reducing color shift and/or organic light-emitting display devices employing the same.
2. Description of the Related Art
Organic light-emitting diodes (OLEDs) include an anode, an organic light-emitting layer, and a cathode. Here, when a voltage is applied between the anode and the cathode, holes are injected into the organic light-emitting layer from the anode, and electrons are injected into the organic light-emitting layer from the cathode. At this time, the holes and the electrons, which are injected into the organic light-emitting layer, are recombined in the organic light-emitting layer so as to generate excitons, and the excitons emit light while transitioning from an excited state to a ground state.
In such an OLED, a lifespan problem resulting from deterioration due to a luminescent material, which is an organic material, is key in developing OLED technology, and many techniques have been introduce to overcome this problem.
A technique using a microcavity structure, which is one of the techniques to overcome the lifespan problem, causes light that is being emitted and has a specific wavelength to resonate, so as to increase the intensity of the light and emit the light to the outside. That is, in the technique, a distance between an anode and a cathode is designed to match with a representative wavelength of each of red (R), green (G), and blue (B), so that only a corresponding light beam resonates and is emitted to the outside and other light beams are attenuated. As a result, in the technique, the intensity of the light beam emitted to the outside is increased and sharpened, thereby increasing brightness and color purity. In addition, the increase in brightness induces low power consumption, thereby increasing a lifespan of the OLED.
However, in a microcavity structure, wavelengths to be amplified are determined based on a thickness of an organic deposition material layer. Here, a length of a light path changes at lateral sides, thereby causing an effect similar to a change in the thickness of an organic deposition material layer. Therefore, wavelengths to be amplified are changed.
In other words, as the viewing angle is tilted from the front to a side, the maximum resolution wavelength becomes shorter, and thus a color shift occurs as the maximum resolution wavelength decreases. For example, even if white color is embodied at the front, the white color may become bluish at a lateral side due to blue shift phenomenon.